1. Field of Invention
The present invention relates to a method for forming a trim cover assembly for an automotive seat, and a device for carrying out such method.
2. Description of Prior Art
In conventional trim cover assembly for an automotive seat, plural patterns of recessed grooves (a')(a')(a') formed on its surface are used for the purpose of improving the outer appearance of the seat, as shown in FIG. 1(A). This sort of trim cover assembly (C) is of a three-lamination type comprising a top cover layer (I) (made of woven fabric, synthetic resin leather, etc.), a foam wadding (2) (preferably a slab urethane foam material), and a wadding cover (3) (preferably a non-woven fabric). These three layers material (I)(2) (3) are locally pressed and welded together by a high-frequency welding device as shown in FIG. 1(B) to form the illustrated patterns of stripe-like recessed grooves (a')(a')(a').
The formation of such patterns is effected by a conventional method using an upper die (U) and a lower die (R), which consists of the steps of placing the three layers, i.e. the top cover layer (1), foam wadding (2) and wadding cover (3) on the lower die (R), in this order, and then the upper die (U) is lowered to press and weld the three layers (1)(2)(3) at the points corresponding to plural projected electrode portions (10) . . . to form such patters of recessed grooves (a') . . . on the top cover layer (1).
However, this conventional method has been insufficient to achieve a clear-cut profile of each pattern (a'). That is, as seen from FIGS. 1(A), each resulting pattern (a') does not result in clear-cut corners and loosens to form undesired arcuate corners.
Another solution to this problem, referring now to FIGS. 1(C) and 1(D), has been proposed, which employs another improved high-frequency welding device comprising a flat upper die (U') and a suction-type lower die (R') having plural equidistant projected electrodes (11, 12, 13 . . . ) as shown in FIG. 1(C). The lower die (R') is formed in a box-like configuration having a hollow therein, having a plurality of suction holes (101 . . . ) perforated in the upper wall thereof, each of which is defined in the respective sections partitioned by the foregoing plural projected electrodes (11, 12, 13 . . . ), and a tube (32A) connected to a suitable air suction device (not shown). In this technique, the three-layer trim cover assembly to be formed utilizes a plurality of separate foam waddings (2a)(2b)(2c)(2d)(2e)(2f), each being of a clear-cut square shape in section. The top cover layer (1) and wadding cover (3) are the same with those of the foregoing first prior art. In brief, the forming steps consist of firstly placing the top cover layer (1) on the plural projected electrodes (11, 12, 13 . . . ) of lower die (R'), then forcibly attracting the top cover layer (1) to the lower die (R') as well as to the plural projected electrodes (11, 12, 13 . . . ) by sucking air through the suction holes (101 . . . ) through operation of the air suction device, next placing the separate waddings (2a, 2b . . . ) and wadding cover (3), in this order, upon the top cover layer (1) thus secured to the lower die (R'), and finally subjecting those three layers to a high-frequency welding, with a pressure plate (P) lowered to press them against the lower die (R'). This approach makes more effective in rendering clear or distinct the resulting pattern of recessed grooves in the trim cover assembly, owing to the forcible attraction of the top cover layer (1) to the lower die (R') and the separate waddings (2a, 2b . . . ).
But, this particular second prior-art technique is still insufficient to attain a completely clear-cut corners on each pattern produced thereby, because of such clearances (H) being created symmetrically relative to each of the projected electrodes (11, 12 . . . ), as depicted in FIG. 1(D), even though the the top cover layer (1) is drawn to the upper surface of the lower die (R). Consequently, the clearances (H) result in the top cover layer (1) pressing the corners of each separate padding (2a, 2b . . . ) and making them arcuate, with the result that the four corners of resulting patterns of recessed grooves (see FIG. 8 for reference only ) do not result in clear-cut or distinct corners conforming to those of rectangular profile of each separate padding (2a, 2b . . . ). This impairs the aesthetic appearance of seat.